Polyvinylchloride foils, which can comprise reinforcements in the form of a mat of glass fibers, a screen or grid of other material, reinforcement fibers of various types, etc., can be provided with pattern-forming impressions or prints during fabrication by a costing process. The foils or sheets can be made by classical methods whereby the vinylic liquid composition of polyvinylchloride base, together with plasticizers and various other additives, is formed into a sheet configuration and solidified at an elevated temperature, generally about 150.degree. to 180.degree. C. in order to effect a gelification or gelling of the material. This gelification can be effected in an oven or carried out by contact of the liquid sheet with a highly polished heated cylinder or drum at the desired temperature. The gelification is carried out contemporaneously with the formation of a surface to which a pattern can be applied by embossment or printing.
The gelification cylinders or drums are utilized in the industrial production of polyvinylchloride floor and wall coverings and for the production of sheets of vinylic materials of different compositions.
Most of the polyvinylchloride based plastic products in sheet form, namely, sheet, awning, curtains, canopies, floor coverings, wall coverings etc. are provided with a decor formed by printing the foil in a plurality of colors.
Such prints can be made by various techniques, e.g. heliography, offset, silk screening using a flat or rotary screen, flexography, . . . , all of which are utilized generally after gelification of the plastic support substrate to be decorated.
The direct printing of a plastic support which is not gelified or which has not been gelified and which will be gelified subsequently, has a number of disadvantages, not the least of which is the dimensional instability of the support which leads to distortion or deformation of the pattern which is applied by printing when gelification is effected.
Naturally it is theoretically possible to integrate in the gelification device a unit for printing the plastic support so as to produce decorative coverings in a continuous manner. However, this has not been found to be practical for a variety of reasons, including the high investment cost which the combination of a printing machine with a gelification machine must involve. The costs include the expenses in preparing the matrices or printing drums or rollers necessary to apply each color to the support to be decorated. For example, if a five color pattern is to be applied to the polyvinylchloride support, five printing drums or matrices are required with respective inking or color application units.
The integration of a printing unit with the gelification unit is thus not justifiable on economic grounds and also poses problems which may interfere with the production of the plastic foil.
Furthermore, if printer systems are provided in separate lines for the plastic sheet material, the cost of handling and producing decorative sheet material with such systems is increased as well.
Moreover, when the patterning system is not integrated with the production of the foil, it is necessary to roll up the foil before printing and to unroll the foil for the printing operation, both being time consuming handling operations.
It has been proposed heretofore to apply patterns to such foils by transfer processes utilizing decalcomania, i.e. patterns which are carried by a paper sheet from which the pattern is transferred to the plastic foil.
The paper utilized in this case is treated, before printing, with special compositions which enable the ink normally used for printing on polyvinylchloride, generally inks or dyestuffs which are polyvinylchloride and polyvinylacetate copolymers, such that these inks or dyestuffs adhere only feebly to the paper and can be transferred hot to the plastic support to be decorated.
In other words, the decalcomania carrier or substrate is pretreated with an agent which promotes release of patterns printed on the paper support onto the synthetic resin foil.
This transfer operation is generally carried out at a temperature between 100.degree. C. and 180.degree. C. and under slight pressure.
The printed face of the paper and the face of the plastic support to be decorated are maintained in contact over a short period sufficient to enable the transfer of the pattern from the paper to the plastic support to take place.
This operation requires equipment capable of bringing about intimate contact at the desired temperature between the pattern carrying paper and the preformed plastic support to be patterned and the machines which have been proposed for this purpose are so called doubling or lining machines of the type developed for the plastics and rubber industries of which I can mention the Auma, Rotodorn, Rotocure types and like machines. The speed of transfer generally is relatively high and can be between 20 and 50 meters per minute. In other words, the linear speed of the two sheets during contact to transfer the pattern is between 20 and 50 meters per minute.
After a slight cooling to about 50 to 80 degrees heat, for example, the paper is separated from the plastic support leaving the transferred pattern intact upon the latter.
This system has the advantage that it allows transfer of a multicolor pattern in one step to the plastic support, but the disadvantage that in the past it has not been effectively integrated with the production of the plastic support.